The constraints on the maximum C_HII and minimum f_esc parameters in order to have the Universe reionized by LBGs at z = 7 given our LF. Given a value for f_esc, the Universe is reionized if C_HII is lower than the red line, if a compact morphology is used (template 5), or lower than the blue line if an extended one is considered (template 4). The ρ_UV is computed integrating the LF down to M₁₅₀₀ = −10 mag. The solid line at C_HII = 1 indicates a homogeneous IGM, and we must consider only the C_HII ≥ 1 region, since galaxies at z ~ 7 are formed in biased density regions of the Universe. The dashed line shows the value C_HII = 3. In practice, only a combination of (f_esc, C_HII) parameters inside the shaded regions corresponds to a z ~ 7 IGM kept ionized by LBGs only.